For purposes hereof, the term bolt is generically used to refer to any of a bolt, through bolt, cap screw, machine screw, set screw or stud. A bolt typically has a cylindrical shaft portion and a head portion, referred to as a bolt head. Often the shaft of the bolt is threaded to receive a nut having a corresponding threaded aperture. The bolt head has a planar top, which is in the plane orthogonal to the central axis of the shaft and the bolt head also has an opposing bottom where the bolt head joins the shaft, and a plurality of planar side faces orthogonal to the bolt head, the planar side faces joining the top and the bottom of the head. The planar side faces are a plurality of substantially flat sides of approximately the same dimension defining an across side dimension and intersecting at a plurality of corners. The planar top and bottom of the bolt head are often hexagonally shaped and sometimes square shaped. American National Standard bolts and nuts come in inch and metric sizes. The number of planar side faces of the bolt head correspond to the number of edges of the top and bottom of the head, where an edge corresponds to a continuous linear portion thereof. For example, a square head has four (4) side faces and a hexagonal head has six (6) side faces. The nut has a top and bottom and orthogonal side faces corresponding to the edges of the top and bottom and an aperture through the central axis thereof, such aperture typically being threaded. The planar side faces of the nut are a plurality of substantially flat sides of approximately the same dimension defining an across side dimension and intersecting at a plurality of corners.
In order to impart rotational motion to nuts, bolts, via the bolt heads, and similar fasteners, a tool is placed to contact the plurality of planar side faces of the nut or bolt head, as the case may be. Conventional open-end wrenches are often used to impart such rotational motion using torque by applying force against a lever arm. Such open-ended wrenches typically have a wrench head. The wrench head of the conventional open-ended wrench is comprised of a jaw having a first jaw member, an opposite facing second jaw member and a throat. In this manner, the two jaw members of the open-ended wrench head can be placed in contact with two, opposite facing faces of the bolt head or nut, with the bolt or nut being received generally in the throat of the wrench head. Closed or box-end wrenches also have a wrench end, but with a closed end enclosing the throat and jaw members.
Disadvantageously, nuts, bolt heads and similar fasteners are often located in areas with very limited accessibility. Unlike ratcheted tools, conventional open-end that are fixed to a handle have limited freedom of rotational movement. To deal with this, often the opening of an open-end wrench is offset at angle relative to the handle. The offset is fixed at anywhere from 15 to 60 degrees. However, this does not solve the obstacle problem, but only allows the user to engage the fastener head at a different approach angle with the hope of extending its rotational movement by avoiding obstacles. Further, both open-end and closed-end wrenches have the disadvantage that once the plane of the jaw orthogonal to the opposing faces of the jaw members is placed in the same plane relative to the top and bottom of the nut or bolt head, as the case may be, there is no mechanism that keeps the wrench head in that plane. As a result, the jaw of the open-end and closed-end wrench head can easily slip up or down, thus losing contact with the side faces of the nut or bolt.
A socket wrench, more commonly referred to as a ratchet, is a type of wrench, or tightening tool that uses separate, removable sockets to fit many different sizes of fittings and fasteners, most commonly nuts and bolts. The socket wrench includes a ratcheting mechanism that allows the nut to be tightened or loosened with a reciprocating motion, without requiring that the wrench be removed and refitted after each turn. Typically, a small lever behind the socket switches the wrench between tightening and loosening mode. The sockets are attached to the ratchet through a square fitting that contains a spring loaded ball detent mechanism to keep the sockets in place. These drive fittings come in four common sizes: ¼ inch, ⅜ inch, ½ inch, and ¾ inch (referred to as “drives”, as in “⅜ drive”). Despite being denominated in inches, these are international standards and no metric counterparts exist. Larger drive sizes i.e. ¾ inch, 1 inch and above are usually reserved for use on fasteners used on larger industrial equipment, e.g. in shipyards. The sockets themselves come in a full range of inch (SAE) and metric sizes. Users are advised that the two should not be substituted for each other, even if the fit seems “close”—as it may destroy the nut or bolt head. The sole exception is the ¾″ and 19 mm sockets, which vary by only one twentieth of one millimeter (less than the width of a human hair).
Extensions, sometimes called “extender arms”, allow access to nuts that are difficult to reach, typically in automotive applications. A breaker bar is an extended-length tool handle for socket wrenches that adds extra torque for loosening strongly tightened or frozen fasteners. Universal joints are two articulated socket joints combined at a right angle that allow a bend in the turning axis of the wrench. They are used with extensions for turning a bolt or nut at a difficult to access location. Flex tool handles are socket wrenches in which the drive head pivots back and forth on the tool handle, to allow the tool handle to avoid obstructions when being turned in a cramped space. Adapters allow sockets of one drive size to be used with wrenches of another drive size. They consist of a male drive fitting of one size attached to a female drive fitting of another size. For example, a ¼ in. to ⅜ in. adapter allows sockets with ¼ in. drive holes to attach to ⅜ in. wrenches.
To overcome the disadvantages of the open-ended wrench, a user may use a ratchet and socket assembly which allows the socket to maintain constant contact with the nut or bolt head while enabling the ratchet body to return to the starting point. However, the use of a ratchet and socket assembly is extremely limited because it is generally cumbersome and large, due to the internal mechanical components of the ratcheting mechanism. As such, the ratchet often cannot be used because it is too large to fit over a fastener's head due to the limited clearance relative to an obstacle.